Priming system for centkifugal



March 10, 194-2. F. s. BROADHURST 2,275,500

PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Fild March 8, 1939 4 Sheets-Sheet 2wz s/vm? 117777585, V k S i g F5a72 ,Zsaaq ans wrf/vraf? 4 Sheets-Sheet3 Marh 10, 1942. F. s. BROADHURST PRIMING SYSTEM FOR CENTRIFUGAL PUMPSFiled March 8, 1939 wwm NM Emzi Sflraadu March 10,1942. F. s. BROADHURST2,275,500

PRIMING SYSTEM FOR CENTRIFUGAL PUMPS Fi'led March 8, 1959 4 Sheets-Sheet 4 x g, f

mmnmmu F I 224% 2/4 I 206 226 h l J 204 2 2 F7421 sigma/2m! 1770 IVEYJPatented Mar. 10, 1942 PRIMING SYSTEM FOR CENTRIFUGAL PUMPS FrankS.,Broadhurst, Watertown, Mass, assignor to De Laval Steam TurbineCompany, Trenton, N. J a corporation of New Jersey Application March 8,1939, Serial No. 260,469

14 Claims.

This invention relates to priming systems for centrifugal pumps.

In cases where there is no supply of liquid availableto prime acentrifugal pump by gravity flow, or where it is undesirable orimpossible to prime the pump by the use of an auxiliary Water pump, ithas been customary to provide the centrifugal pump with an air pump inthe same casing to evacuate the main pump and so render it self-priming.A system of this character is very unsatisfactory for several reasons,among which may be mentioned the fact that the centrifugal pump isdriven for an appreciable time without priming, which may result indamage to labyrinthine packing, the fact that there is absorption ofconsiderable power by the air pump which is running throughout theoperation of the main pump, and the fact that scoring and plugging ofthe air pump may occur due to grit, dirt, seaweed, etc. in the Waterbeing pumped, some of which is passed through the air pump for sealingpurposes. i Ithas also been customary to prime centrifugal13111111351011 the delivery side, sometimes with the provision of floatvalves or the likedesigned to prevent the passage of liquid to. a vacuumpump after the centrifugal pump is primed and operating. The valvesunder such conditions are exposed to high pressures and are liable todamage by impact and blocking by solid or semisolid material jammedagainst them, for example, in the handling of sewage.

In general pumping, and particularly in the pumping of driven walls, airis carried into the centrifugal pump with the liquid. This air isseparated by the centrifugal action of the pump and accumulates adjacentthe shaft. When the accumulation reaches such extent as to substantiallycut off the intake passages, the pump will loselits prime and withprevious priming systems it was. necessary to shut down, the pump,reprime, and then restart the pumping operations.

In my application Serial No. 11,867, filed March 19, 1935, there aredisclosed priming arrangements for centrifugal pumps which overcome theaforementioned objections to prior priming arrangements. The presentinvention relates to priming systems of this general type in whichpriming is efiected byevacuation of the suction side of. a centrifugalpump. The present invention, however, involves various improvements onthe systems described in my prior application whereby the operation ofthe vacuum pumpsis still further reduced, normal operation, even thoughit involves a considerable accumulation of gas, being accompanied withno operation of the vacuum pump or pumps unless abnormally highquantities of gas enter the system. Under normal conditions, theevacuation only takes place in the initial priming of the system onstarting. Thereafter accumulated gas is removed automatically by theaction of the centrifugal pump itself.

Subsidiary to the broad object of the invention just indicated arevarious secondary objects having as their ends the proper rapid andreliable operation of the priming system to take care of moderncentrifugal pumping installations which are designed to operateautomatically over long periods with little or no attention.Specifically, the subsidiary objects of the invention relate to theprovision of arrangements for taking care of abnormal gas accumulation,for handling water carrying sediment or floating material, and formaintaining proper operation despite surges attending unusual conditionsin the supply or discharge lines. Additionally, provision is made forthe operation of pumps in parallel or the operation of pumps receivingtheir liquid from different supplies, and particularly undercircumstances in which any one or more of a series of pumps primed by acommon system may be subjected to an abnormal accumulation of gas.

In such case the other pump or pumps may Figure 3 is a wiring diagramshowing the electrical connections in the arrangement of Figures 1 and2;

Figure 4. is a view similar to Figure 1, but illustrating a modifiedform of the invention;

Figure 5 is a similar view, partly in section, but showing the inventionapplied to the priming of a plurality of centrifugal pumps;

Figure 6 is a diagrammatic View illustrating still another modificationof the invention particularly applicable to the pumping of liquidcontaining relativelylarge quantities of gas or dirt,

of the pump. Figure 2 shows a section of a portion of the upper casingof the centrifugal pump,

which, in the illustration is a double suction pump, the suction :bellsbeing indicated at it and the discharge volute being indicated at M,though it will be obvious that the invention is applicable to a singlesuction pump and to multiple stage centrifugal pumps as well as the typeillustrated. The impeller of the pump indicated at E2 operates in thepump casing of which the discharge volute M is a part. The pump isassociated with the conventional valves including the usual dischargecheck valve.

At the top of each of the suction bells there is provided a connectionto a pipe I6, preferably of substantial diameter. For example, this mayhave a diameter of 1% inches. A large diameter pipe is desirable at thispoint to provide for the free upward passage of gas. The pipes itcommunicate with a chamber l8, which may take the form of a rectangularbox. Extending from the top of this chamber l8 are tubes 20 passingthrough thepipes l6 and terminating as indicated at 22 closely adjacentthe shaft of the centrifugal pump.

Extending from the top of the chamber 13 there is the evacuating passage24 communicating with a water jet air pump indicated at 28, there beinginterposed-in the connection 24 a check valve 28 adapted to preventreverse flow of fluid back to the chamber l8. The water jet air pump isprovided with supply Water under pressure through a passage 39controlled by a valve 32 actuated by a solenoid indicated at 34, thevalve being closed when the solenoid is actuated. The discharged liquidand gas from the water jet air pump are discharged through conduit 36.

Supported in a holder at the top of the: chamber it are electrodes 38and 4B, the former of which is substantially longer than the latter.These two electrodes are the control electrodes for a relay which isillustrated as of the wellknown Bender-Warrick induction type. This typeof relay is provided with an A-shaped core indicated at 6.2 having acoil 44 on its crossbar portion grounded at one end and connected at itsother end to the electrode 49. The upper connecting element of the coreis provided with a coil 46 permanently connected to an alternatingcurrent power line. The legs of the core are adapted to attract anarmature 48, which is conventio'nally illustrated as adapted to close asingle contact at 50, and thereby connect the electrodes 38 and MItogether, and a pair of contacts 52 adapted to cause the energization ofthe solenoid 34, which controls the valve 32, and also effects theremoval of a short circuiting connection for the no-voltage release ofthe starter 56 for the pump motor 2, this being .accomplished through asuitable relay, which is not shown. The relay may be convenientlyenclosed in a box 5% secured to the chamber l8 and connections madethrough an electrical outlet boX indicated at 613.

Operation of the modification so far described is as follows:

Assuming that the pump is unprimed, the armature 48 will not beattracted by the field member of the relay because the flux produced bythe coil it will have its magnetic circuit completed through thecrossbar carrying the open-circuited coil 44. The solenoid 34 will,therefore, be deenergized and the valve 32 will be opened. Theno-voltage release coil of the starter will be deenergized, andconsequently the motor 2 cannot be started.

To start the operation of the unit, water from the air pump supply iscaused to flow through the conduit 39, thereby drawing a vacuum inchamber I8. Due to this action, the liquid will be lifted through theinlet 6 into the centrifugal pump (the usual check valve on its deliveryside being closed), and will rise through both sets of tubes i6 and 22immersing the lower end of the electrode 38. Nothing will happen,however, since the electrode 38 is open-circuited at 5B. As soon,however, as the liquid reaches the level of the electrode 43, the coil4%, now acting as the secondary of a transformer, will have its circuitcompletedthrough the liquid to ground. Consequently, acounter-magnetomotive force is created opposing the flux through thecrossbar so that the flux will tend to take a path through the armature48, attracting this armature and closing the contacts at 50 and 52. Assoon as the contact at 50 is closed, electrode 33 is thrown in parallelwith the electrode 40 and Will additionally tend to maintain the closedcondition of the relay. At the same time, the solenoid 34 is energized,closing the valve 32 and removing the short circuiting connection fromthe no-voltage release of the motor starter.

The pump is now primed and the motor is ready to start. Starting may beeffected by a hand control of the starter; or; alternatively, thearrangement may be readily made such that upon energization of theno-voltage release coil the motor will start automatically. Since thespecific arrangements for automatically starting a motor are no part ofthe present invention, this may be considered as embodied in thediagrammatic illustration of the starter at 56.

Before passing to the centrifugal pump operation and primingconsiderations, it might be here noted that the arrangements of the twoelectrodes 33 and 40 prevent unstable operation since, though thestopping of the vacuum producing means is not effected until theelectrode 40 is submerged, the vacuum producing means will not berestarted until the liquid level drops below the lower end. of theelectrode 38, inasmuch as this electrode, through the closure of itscircuit at iii), acts as a holding control, maintaining the armature 48in its attracted position. The height between the lower ends of the twoelectrodes defines a region'through which fluctuations of liquid levelmay occur without'disturbance to the system. This distance should bemade such that normal fluctuations in liquid level due to surges orother cause will not result in restarting of the vacuumproducing .meansor stoppage of the driving motor 2. On the other hand, whenever theliquid drops below the level of the electrode 38, the motor 2 willimmediately stop, due to short circuiting of the no-voltage release, andwill not then restart until the electrode 49 is submerged.

The action just described would obviously be unsatisfactory ifcontinuous priming, i. e., continuous removal of gases did not takeplace independently of the water jet air pump 28. As a matter of fact,the arrangement of the pipes l6 and 20 effects continuous removal ofnormal amounts of gas which might accumulate by the action of thecentrifugal pump itself.

Assume that priming has taken place with the resulting rise of theliquid to the level of the electrode 40 and that the motor 2 has thenbeen started either manually or automatically to drive the centrifugalpump. The check valve 26 will have closed upon interruption of flow ofthe air pump operating liquid through 30 by the action of valve 32.

It will be noted that the lower end of the electrode 40 is substantiallybelow the upper ends of the tubes 21:, providing a substantial gasspace. As the liquid flows into the impeller from the suction bell,asuificiently high velocity is created due both to the approach andtherotation of the liquid in the bell by the shaft as to create asubstantial ejector action at the lower ends 22 of the tubes 29 wherethey approach theshaft. A partial vacuum is thus produced which intypical installations may be of the order of about 4 feet of water. Theoreation of this partial vacuum removes the gas from the space at theupper end of the chamber l8 in such fashion that the gas is entrained infine bubbles in the water in the suction bell and is hence carriedwithout separation to the impeller l2 to be discharged thereby. Thisprovides a rise of liquid from the suction bells through the pipes 16and withinthe chamber I8 to the upper ends of the tubes 20, whereuponduring continued operation there occurs a recirculation of liquid fromthe suction bells into the chamber and thence through the tubes 20 totheir lower outlets adjacent the shaft. A differential pressure of theamount indicated is thus continuously maintained between the upper endof each of the suction bells and the lower ends 22 of the tubes 20. Ifgas accumulates and floats upwardly through the pipes IE, it will beremoved immediately by reason of this ejector action and consequentlythe liquid level during normal operation with normal amounts of gasentering the device will remain near the'upper ends of the tubes 20.

If larger amounts of gas enter with the incoming liquids, it is possiblethat this .gas may be separated centrifugally within the suction bells,with the result that the lower ends of the tubes 20 may be surrounded bygas rather than liquid. As soon as this occurs, the ejector action atthe tubes 2|] will cease and consequently an equalization of pressurewill occur in the systemsubject only to the centrifugal action whichtakes place. The static head of the liquid, however, above the suctionbell will cause the gas surrounding the lower ends of the tubes 20 to beforced upwardly therethrough into the upper portion of the chamber I8,producing a drop in the liquid level therein. Since the chamber l8 has avolume substantially greater than the total volume of the suction bells,it will be obvious that the liquid level will not drop to any greatextent before the lower ends of the tubes 20 are again exposed to liquidwith a renewal of the ejector. action. The accumulated gas will then berapidly drawn off in a fine state of subdivision so as to pass into theimpeller without reseparation, and consequently the liquid notbeexpected to occur for a long interval.

. of the pipes I6 will be obvious.

level willbe restored to normal at the level of the upper ends of thetubes 20;

As a result of the ejector action, and also the possibility of removalof centrifugally separated large quantities of gas, the continuousremoval ofaccumulated gas takes place with the result that only ,underthe most abnormal conditions will the liquid level in the chamber l8fall below the lower end of electrode 38 to close down the system. Undersuch conditions, as soon as the electrode 38 is cleared by the liquid,the jet air pump will reprime the system and, if the motor 2 isautomatically controlled, it will restart as soonas the electrode 49 issubmerged.

If the motor 2 is not arranged to be self-starting, then it is desirableto have some signal indicate the stoppage of the system to an operator,who may thereupon promptly restart it if the causeof the loss of primehas been corrected. In thecase of bilge pumps it is desirable to havemanual starting since the failure of prime will be generally due to theremoval of all the liquid in a bilge, and necessity for restarting wouldThe tubes 29 preferably extend upwardly near the top of the chamber I8so as to leave a minimum air space at the top of the tank preventingdrop of liquid level to any substantial degree upon the occurrence ofsurges.

While reference has been made to priming with the motor stopped (as isgenerally desirable with centrifugal pumps) it will be clear that theprim ing system will opera e just as well with the motor runningjas maybe the case in some instances ;where such type of priming is desirableand the centrifugal pump is of a type which will not be damaged by dryrunning for substantial periods of time. Ifthe motor is run-- ning wheninitial priming is taking place, the removal of centrifugally separatedgas will take place as indicated above, withthe ultimate result that theconditions heretofore described will be established.

The reason for the relatively large diameter A large passage for theupwardly floating gas is desirable for its rapid accumulation at the topof the chamber l8. This should be free to occur without any possibilityof having the passages through pipes I6 contain plugs of gas. On theother hand, the tubes 22 may be of relatively small diameter, since thena better ejector action is secured with a resulting fine dispersion ofthe gas so that it will be carried along by the liquid without againseparating in the suction bells.

In Figure 4 there is illustrated a modification of the arrangement justdescribed which is essentially the same as that modification except forprovision for priming under conditionswhen a high pressure water supplyis not available for actuating the water jet air pump. In thismodification of Figure 4, the vacuum connection 24 is connected throughthe check valve 26 to a water jet air pump indicated at 62. This isarranged to discharge into a vessel 64, the discharge taking placethrough the pipe 66 opening within a chamber separated by a bafile 68 soas to provide for the more ready separation of the exhausted gas andprevention of passage of this is automatically controlled by the sametype of electrical connections as were used for the control of thesolenoid 34 in the previously described modification. In this case,however, the starting box is so arranged under relay control that themotor I2 will be started whenever the longer electrode 38 is uncoveredby liquid and will be stopped only when the electrode 40 is submerged.Thus the motor I2 and the water jet air pump will be actuated only whenit is necessary to draw a vacuum under the conditions described inconnection with the previous modification.

The two modifications heretofore described will make clear the moregeneral application of the invention to the use of various vacuumproducing devices for effecting priming. Any suitable type of wet airpump might be substituted for the water jet air pumps described, and maybe subjected to suitable control by the electrodes 38 and 48, as will beobvious. The vacuum connections illustrated, however, would necessitatea wet type of air pump. A dry type could not be directly used becausethe connections are of such nature that liquid may enter the pump. If adry type of pump is to be adopted, then provision must be made toprevent passage of. liquid to the air pump. Arrangements for this willnow be described in connection with the modifications of Figures 5 and6.

Considering first the modification of Figure 5, there is illustratedtherein an arrangement for the priming of a plurality of centrifugalpumps by means of a dry type vacuum pump. In this modification there areillustrated at 16 and 16' motors driving centrifugal pumps 18 and 18',which may be of any suitable type as indicated above. These pumpsreceive their liquid through the conduits 88 and 80, respectively.-

The pump 18 has extending through its suction bells and closely adjacentthe shaft a pair of tubes 82 corresponding to the tubes 28 of thepreviously described modification. This pump also has communicating withthe tops of its suction bells tubes 84 which correspond to the tubes I8of the previous modification, but which are illustrated as notconcentrically arranged with the tubes 82. (It will be understood thatthe concentric arrangement of the previous modification plays noparticular part in the operation and merely serves for convenience ofmounting of a small chamber such as I8.) The tubes 82 are preferably ofsmall bore and the tubes 84 of large bore for the reasons indicatedabove in connection with tubes 20 and I6. The pump I8 is provided withtubes 82' and 84', respectively similar to tubes 82 and 84.

The tubes 82 and 82 are connected to a header 88 which is joined bytubing 88 to a wet chamber 98 located at a level substantially above thepumps. The connection 88 enters this wet chamber substantially above itsbottom as indicated. The tubes 84 and 84' are joined to a header 92which is connected by a tube 94 withv the bottom of the wet chamber 98.The wet chamber 90 may be built as a, unit with a dry chamber I00,separation being provided by a wall IIlI, though it will be obvious thatchambers which are structurally completely separate may be provided. Avalve 98 controls flow of gas from the chamber 99 to the chamber. I88,this valve receiving gas from the chamber 90 through a tube 98, whichopens at the extreme top of the chamber 98 to thereby avoid thepossibility of the passage of any substantial quantity of liquid intothe chamber Hill. The valve 98 is controlled by a float I82, being openwhen the fioat is in its'lower position and closed when the floatreaches an upper position in which it is arrested by a stop I84. Thearrangement is preferably such that the tube 88 communicates with thechamber 98 above the top of the float I82 when in its arrested positionso that when liquid rises to the level of the tube 88 the float will beheld'by its full buoyant force against the stop I64 to therebyinsurethat it will not bob up and down with slight fluctuations in the liquidlevel. Preferably it will have closed the valve 96 completelysubstantially before rising to its ultimate level.

Accumulation of liquid in the chamber I00 cannot be completely preventedsince it will be carried over not only as fine spray, but moreparticularly in the form of vapor which may condense in the tank I88.Since, as in this case, the pumps may be of a type which cannotpermissibly handle an aqueous liquid without damage, provision should bemade for removing any accumulated liquid from the tank 28 from time totime. In the present case, this takes the form of a water jet ejectorI88 connected at I86 to the bottom of the tank I88 with theinterposition of a check valve I81 adapted to close and maintain thevacuum in the tank I08 when the jet pump is not operated. The supplyline for the jet pump is indicated at III) and may be manuallycontrolled. The discharge is through the pipe II2 into the wet chamber98. Under usual conditions of operation, this jet pump need be operatedonly for very short periods at long intervals. A gauge glass may beprovided to indicate any accumulation of liquid in the tank I00.

A vacuum is maintained within the chamber I00 through connections H4 andH4 containing check valves H5 and H5 by means of vacuum pumps H8 and H8driven by motors H6 and HE. A pair of these vacuum pumps H8 and H8 isillustrated, since some installations require a very great factor ofsafety and it is desirable in such case to duplicate the vacuum pump toinsure against failure of operation. The vacuum pumps in the presentcase are illustrated as of the Imo type, i. e., comprising a pluralityof screws arranged to be motor driven and sealed to provide air pumpingpassages by means of oil contained in a tank indicated at 128. Pumps ofthis type are positive pumps capable of handling large quantities of airwhich may be separated from the recirculating oil by means of a screenarrangement indicated at 22 and thence pass outwardly through a pipe I24which may pass to a device for further insuring separation and avoidingloss of oil. These pumps, while using oil for sealing purposes, would beclassified as dry pumps, since they are apt to be damaged by anon-lubricating liquid such as water.

The motors H6 and H5 are under the control of vacuum switches I26 and I28 communicating With the tank I 88 and controlling the motors through amotor starting box I38. The two vacuum switches are again provided forsafety purposes. One of them, for example, may be effective to start themotors at a vacuum of 18 inches of mercury and stop the motors at 26inches of mercury, while the other may start the motors at a vacuum of16 inches and stop them at 26 inches. Thus the former will normally bethe controlling switch, while the latter serves to effect its controlonly under emergency conditions.

Both of these should be of the snap type, as indicated, to avoid anyinstability of operation.

. A low water cutoff indicated at I32 may be used for control of thecentrifugal pumpmotors to prevent their starting before the liquid risesto a predetermined level in the tank 90 and to cause them to stop if theliquid drops below such level. This low water cutofi may be either floatcontrolled or may be of the electrode controlled type previouslydescribed.

In the operation of the modification of Figure 5, assuming thecentrifugal pumps stopped, the priming may be initiated by closing themain switch controlling the motors H6 and I I6. The valve 96 will now beopened due to the lower position of the float I 02 and hence a vacuumwill be drawn on the system causing the liquid to rise in thecentrifugal pumps through the tubes 82 and 84, headers 86 and 92 andthen the tank 90. As the rise of liquid continues, the low water controlI32 will be actuated to either start automatically the motors I6 and I6or to render it possible to start them manually. Eventually the floatI02 will close the valve 96, thus preventing further entrance of gasinto the tank I 00, whereupon the pumps II 8 and 8' will continue tooperate until the vacuum switches stop them by reason of the drawing ofa high vacuum in the tank. As operation proceeds, the ejector actiondescribed in connection with the previous modification will take placeat the lower ends of the tubes B2and 82, resulting in further evacuationof gas from the chamber 90 and rise of liquid to force the float I02against its stop I04. Thereafter the liquid will rise to the level ofthe connection 88 and recirculation will then take place upwardlythrough the tubes 84 and 84' and downwardly through the tubes 82 and 82.As small normal quantities of gas accumulate in the tank 90 this gaswill be drawnoff without producing any dropping of the float I02 and,therefore, without opening the connection to the vacuum tank I00.

In the event that air is centrifugally separated in considerable amountwithin the intake bells of either of the pumps, this air will firstescape 90 is of considerable size, there may still be no opening of thevalve 96. A substantial amount of air may flow into the tank 90 withoutcausing the float I02 to move away frim its stop.

In the event that a plurality of pumps are provided, it will be seenthatall contribute to the maintenance of the primed condition of any oneof them. Consequently, even though one may receive. a substantiallylarge quantity of gas, this gas will be rapidly removed by the action ofthe others, in fact without ever reaching the tank 90, since the ejectoraction in a companion pump or pumps will merely cause recirculation ofthe gas upwardly through the tubes 82 in the pump from which the gasflows, into the header 86 and downwardly through the tubes 82 of thepump or pumps which continue to operate normally.

As a result of the arrangement described, the

vacuum pumps H8 and H8 will operateusually only in starting up thesystem. They will resume operation only if such a large quantity of gasenters the tank 90 as will produce an opening of the valve 96 andreduction of the vacuum to an extent suflicient to throw one of thevacuum switches. By reason of the fact that the system of this by thewater jet air pump I08 need be elfected only at long intervals.

At this point it may be remarked that the tubes 82 or 20 may be soformed at their lower open ends as to secure various efliciencies in theejector action. In the event that they open in a direction perpendicularto the shaft, the ejector action is quite sufficient for most purposes,being, for example, such as to produce a vacuum of the order offour feetof water relative to the pressure in the suction bell. At the same time,they will remove rapidly any gas which may accumulate centrifugallyabout the shaft. A more eiiective ejector action may be secured if thelower ends of the tubes 82 open closely adjacent the shaft, but in thedirection of circulation about the shaft, thus giving rise to a Pitottube action.

Under such conditions, however, the separation of centrifugallyaccumulated gas is not as rapid as before because of the ejector actionof the rotating gas. Such ejector action, however, is far less than,that secured by the passage of the liquid past the lower ends of thesetubes.

In Figure 6 there is illustrated still another modification of theinvention particularly adapted to the case of the pumping of water orother liquid containing sediment and relatively large quantities of gas,for example, in the pumping of driven wells. In this arrangement a motorI34 drives a centrifugal pump I36, the intake passage I38 of whichreceives liquid from the socalled sand tank I40, which is connectedthrough passage I42 with the supply. Within the chamber I40 are bafllesI44 designed to prevent the passage of sediment to the pump, the tankbeing provided in conventional fashion with a clean-out opening (notshown). centrifugal pump I36 is provided with a pair of tubes I46extending through its suction bells to a point adjacent the shaft, thesetubes I46 corresponding to the tubes 20 and 82 of the previousmodifications. In this case, however, there are no tubes providedcorresponding to Hi and 04,

inasmuch as the tank I40 serves for the separation of any gas which, inthe absence of the tank I40, might separate in the suction bells of thepump. The tubes I46 are connected through a common tube I48 to the upperend of the tank I40, the head of which is indicated at UM, there beingbuilt as an upward continuation of it a vacuum tank I56.

Opening just below the top II of the tank M0 is a tube I50 communicatingthrough a valve I52 with the pipe I54 entering the vacuum tank I56. Thevalve I52 is similar to the valve 96 previously described, and iscontrolled by a float I58 the upward movement of which is limited by astop I6I so that when liquid rises to the height of the tube I48 thefloat I58 will be against the stop I60 and substantially completelyimmersed so as, to avoid fluctuations of its level and possible ing asupply of water under pressure through I66 and discharging at I68 intothe tank I40. Asin the case, of the vacuum pump I08 previously de- Thescribed, this vacuum pump serves for the removal of moisture which mayaccumulate in the bottom of the vacuum tank due to the passage of spraythereto or condensation.

From the top of the vacuum tank there extend vacuum lines I72 and I12containing check valves I H3 and I16 and communicating respectively withhigh vacuum pumps driven by motors I'M and IN, this arrangementcorresponding to that described in connection with the modification ofFigure 5.

For the control of the motor Iii-i there may be provided the levelswitching arrangement I'Iii connected to the'tank I40 at I18 and IE0.Instead of a float controlled switch there may be provided an electrodetype arrangement similar to that illustrated in the first modification.In any event, a suitable switching arrangement is provided to insureeither automatic starting of the motor I34 when the liquid rises to apredetermined level or, alternatively, a possibility of manual starting.At the same time, the switching arrangement must provide for stopping ofthe motor I34 in the event of abnormal drop of the liquid level".

The vacuum pumps are under control of vacuum switches I82 and I84connected to a common relay or motor starter I86. These switches may beof the same type and act in precisely the same fashion as the switchesI22 and I28 of the modification of Figure 5. I

The above indication of the correspondence of elements of Figure 6 withthose of Figure will make clear the nature of the operation of themodification of Figure 6. The only substantial difierence is that thecirculation eiiected by the ejector action at the lower ends of thetubes I46 will be from the tank I45) through the tube M8 and tubes Hi6after the liquid level rises to the level of IE8. Any air accumulatingin the tank Idll will be drawn oii through the tube 38. As in theprevious modification, this takes care automatically of any normalaccumulations of air and the float I58 will be permitted to drop to openthe valve I52 only upon an abnormal accumulation of air in the tank Mil.If this occurs, then the air will pass to the vacuum tank H36, Wheresubstantial accumulation will result in renewed operation of the vacuumpumps. Under normal conditions, even with considerable accumulation ofair in the tank M0 the vacuum pumps will not operate except in theinitial priming of the system. If any sufficient amount of air shouldfind its way into the centrifugal pump so as to be centrifugallyseparated in the suction bells the tubes I46 will take care of this airby permitting it to pass into the upper end of the tank I 4-0. As soonas the ejector action is renewed, this air will then be removed by thecentrifugal pump.

In Figure '7 there is illustrated a modification of the inventionapplied to a gravel packed well of conventional type. Such a wellcomprises a casing IQI! which has a lower screen portion I92 throughwhich water may enter. Surrounding the screen portion of the well and ingeneral extending upwardly to the surface, there is a packing of gravelindicated at I 9%. There extends downwardly from the surface an outershield indicated at H33 which is sealed with concrete to a level belowthe normal static water level, indicated at 283. In general, this staticwater level is less than five feet to the center line of the pumps;

Pumping is effected by connecting at 202 to the casing one or morecentrifugal pumps indicated at 204, driven by one or more motors 206 andarranged to discharge through conventional check valves 208.

In accordance with the present invention, the casing I9!) is continuedto a substantial height above theintakes of the pumps, say about fivefeet above the pump house floor. I The extension or the casing as wellas the casing itself may be two or more feet in diameter so that thereis provided by the extension 2H] a quite large diameter which may act asa reserve pump for available liquid to prime the pumps in the event ofany large influx of air.

The extension 2H] is provided with a cover ZIZ. from whichextends a pipe2 I4 to a vacuum tank 216, having wet and dry compartments M8 and 220,respectively. Since this tank and its various associated parts may beidentical with the tank assembly heretofore indicated at Hill in Figure5,

the various parts thereof need not be described.

The dry portion 220 of the tank is connected to vacuum pumps 222, asheretofore described, under control of vacuum switches, and the wetcompartment 2| 8 is connected through pipes 224 to tubes 226 closelyapproaching the pump shafts as previously described, so as to give riseto an ejector action during operation of the pumps.

The operation of this modification is quite similar to that of themodifications previously described. The vacuum pumps create a vacuum tocause the supply liquid to rise into the wet chamber 2I8 until the floattherein closes off the vacuum communication. Thereafter, as the pumpsrun, they maintain by ejector action the vacuum above the level of theliquid in the Wet compartment, causing the float valve to rise againstits stop and produce ultimately a circulation of liquid from theextension 2) of the casing through the wet compartment and to the pumpsthrough the pipes 224 and 225. Thus accumulation of air in the extension2H1 is drawn ofi? without having the communication between the tanks 2I8and 220 reopened under normal circumstances. Even a sudden large influxof air will not interfere with operation by causing the centrifugalpumps to lose their prime because of the large volume provided by thecasing extension. Any such large amount of air which may enter thecasing will be taken care of gradually bythe ejector action and, ofcourse, by the volume pumps if the influx is such as to cause the floatvalve to open. A suitable low level safety. arrangement may be providedto stop the centrifugal pumps in case the liquid level becomesdangerously 10w within the casing extension.

It will be understood that the various elements of the device,particularly the vacuum pumping arrangements, may take various forms.For example, water jet ejectors or even steam jet air pumps may be usedthroughout the arrangement, or either wet or dry types of mechanicalvacuum pumps may be used. In' the event that wet types are used, noprecautions need be taken to avoid the passage of water to the pumps,and accordingly the general type of arrangement indicated in Figure 1can be adopted. The adaptation of this to a sand chamber or tank of thetype indicated in Figure 6 will be obvious, as will also be itsadaptation to the priming of a plurality of pumps.

It will be noted that the various modifications described above have incommon the characteristic of maintaining abovethe pump a quitesubstantial supply of liquid sothat, in effect; the

pump is maintained primed by what is during operation a floodingarrangement. Thus, while the invention contemplates a suction primingsystem, it is differentiated sharply from such priming systems as merelyraise the liquid to the level of the pump, but whichwould permit thepump and subjected to an ejector action of liquid being handled by saidpump to cause rise of liquid in said chamber substantially above saidpredetermined level, said last means comprising a tube opening closelyadjacent the shaft of said pump and subjected to the ejector action ofliquid ad-;

jacent said shaft, and arranged to provide flow of centrifugallyseparated gas adjacent the shaft to said chamber during its evacuationby the first mentioned evacuating means. i

2. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage to thereby prime the pump; means controlled by rise ofliquid in said chamber to a predetermined level to stop the evacuationof said chamber by said means; means connected to said chamber andsubjected to an ejector action of liquid being handled by said pump tocause a rise of liquid in said chamber substantially above saidpredetermined level; and means for effecting further evacuation of saidchamber by the first mentioned evacuating means only when said liquidlevel falls substantially below the level to which it rises under theaction of said last named means.

3. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage to thereby prime the pump; means for stopping theevacuating action of the last means when the liquid has been so raised;means connected to said chamber and subjected to an ejector action ofliquid being handled by said pump to maintain a partial vacuum in saidchamber after evacuation by said evacuating means ceases; and means foreffecting further evacuation of said chamber by the first mentionedevacuating means only when the liquid level drops substantially below anormal level attained under the action of said means subjected toejector action of liquid.

4. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage to thereby prime the pump; means controlled by rise ofliquid in said chamber to a predetermined level to stop the evacuationof said chamber by said evacuating means; and means connected to saidchamber and subject to an ejector action of liquid being handledby saidpump to maintain a partial vacuum in said chamber, said last meanscomprising a tube opening closely adjacent the shaft of said pump andsubjected to the ejector action of liquid adjacent said shaft, andarranged to provide flow of centrifugally separated gas adjacent theshaft to said chamber during its evacuation by the first mentionedevacuating means.

5. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump for accumulationof gas contained in the liquid being pumped; means for evacuating saidchamber to raise liquid therein to a level above the intake passage tothereby prime the pump; means connected to said chamber and subjected toan ejector action of liquid within the intake passage and being pumpedto maintain a partial vacuum in said chamber, said last means comprisinga tube opening closely adjacent the shaft of said pump and subjected tothe ejector action of liquid adjacent said shaft; and means; effectiveto close communication between the chamber and said evacuating meanswhen liquid in the chamber reaches a predetermined level below the levelof connection with the chamber of the means subjected to said ejectoraction of liquid.

6. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage thereby to prime the pump; means controlled by rise ofliquid in said chamber to a predetermined level to stop the evacuationof said chamber by said means, and controlled by drop of liquid toresume evacuation of said chamber by said means; and means connected tosaid chamber and subjected to an ejector action of liquid being handledby the pump to evacuate the chamber to maintain the liquid being handledby said pump to effect continuous removal of gas accumulating in saidchamber to maintain at least said predetermined level of liquid which iseffective to stop evacuation.

8. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage thereby to prime the pump; means controlled by rise ofliquid in said chamber to a predetermined level to stop evacuation ofsaid chamber by said means; and additional evacuating means connected tosaid chamber and effective when the pump is handling liquid to cause arise of liquid in said chamber substantially above said predeterminedlevel and to the connection of said additional evacuating means with thechamber so that liquid flows from the intake passage through the lastnamed means during operation of the pump.

9. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage thereby to prime the pump; means controlled by rise ofliquid in said chamber to a' predetermined level to stop evacuation ofsaid chamber by said means; and additional evacuating means connected tosaid chamber and subjected to an ejector action of liquid being handledby said pump to cause a rise of" liquid in said chamber substantiallyabove said predetermined level and to the connection of said additionalevacuating means with the chamber so that the liquid is circulated fromand vacuum tank when the liquid rises to a predetermined level in saidchamber; and means connected to said chamber and continuously subjectedto an ejector action of liquid being handled by said pump to effectcontinuous removal of gas accumulating in said chamber and to maintainat least said predetermined level of liquid there- 11. In combination, acentrifugal pump; means providing a chamber connected to the intakepassage of the centrifugal pump; means for evacuating said chamber toraise liquid therein to a level above the intake passage thereby toprime the pump, said evacuating means comprising a vacuum tank connectedto said chamber, and a pump for creating a partial vacuum in said tank;means for closing the connection between the chamber and vacuum tankwhen the liquid rises to a predetermined level in said chamber; meansfor stopping the action of the vacuum pumpv when the vacuum in the tankis substantially higher than the vacuum corresponding to rise of liquidto said predetermined level; and means connected to said chamber andcontinuously subjected to an ejector action of liquid being handled bythe centrifugal pump to effect continuous removal of gas accumulating insaid chamber and to maintain at least said predetermined level of liquidtherein. i

12. In combination, a centrifugal pump; means providing a chamberconnected to the intake passage of the centrifugal pump; means forevacuating said chamber to raise liquid therein to a level above theintake passage thereby to prime the pump; means for stopping theevacuating action of the last means when the liquid has been so raised;and means connected to said chamber and subjected to an ejector actionof liquid being handled by said pump to maintain a partial vacuum insaid chamber after evacuation by said evacuating means ceases, said lastmeans comprising a tube opening closely adjacent the shaft of said pumpand subjected to the ejector action of liquid adjacent said shaft.

13. In combination, a centrifugal pump comprising a casing having intakeand discharge passages, a rotor, and a shaft carrying the latter; meansproviding a chamber connected to the intake passage of the centrifugalpump; and means connected to said chamber and subjected to an ejectoraction of liquid being handled by said pump to cause rise of liquid insaid chamber, said last named means comprising a tube opening closelyadjacent the shaft of said pump at the intake side of the rotor andsubjected to the ejector action of liquid rotating adjacent said shaft.

14. In combination, a centrifugal pump comprising a casing having intakeand discharge passages, a rotor, and a shaft carrying the latter; meansproviding a chamber; means connecting a lower portion of the chamber tothe intake passage of the centrifugal pump; and additional meansconnecting the chamber to the intake passage of the centrifugal pumpcomprising a tube communicating with the upper portion of said chamberand opening closely adjacent the shaft of said pump and subject to theejector action of liquid rotating adjacent said shaft.

FRANK S. BROADHURST.

